Excitation of the Auroral Green Line in Nitrogen Afterglows

Abstract

Production of the auroral green line of OI (¹D—¹S, 5577 A) is observed during long (30‐sec) afterglows in a static system containing nitrogen and small amounts of oxygen. Relative to the intensities of the N₂ 1st positive bands, the measured intensities of 5577‐A and the NOβ bands increase with time. The long period of observation definitely eliminates the initial discharge as a possible source of the metastable oxygen atoms, and their chemical excitation in the afterglow volume is established. A probable process consistent with observations is that involving collision of N atoms with vibrationally excited NO molecules. This mechanism is discussed as a possible source of 5577 A in the airglow.